1. Field of the Invention
The invention relates to a disc recording and/or reproducing apparatus. More particularly, the present invention relates to a transport mechanism for a disc recording and/or reproducing apparatus.
2. Background of the Invention
There has hitherto been proposed a disc recording and/or reproducing apparatus in which information signals are recorded on and/or reproduced from a recording disc, as a recording medium, such as an optical disc or a magneto-optical disc.
The disc recording and/or reproducing apparatus includes a rotation mechanism for holding and rotating the recording disc and a pickup unit for writing/reading the information signals on or from the recording disc as it is rotated by the rotation mechanism.
The disc recording and/or reproducing apparatus also includes a disc tray adapted to transport a recording disc set thereon between the outer side and the inner side of a main body of the apparatus. The disc tray is supported on a supporting shaft arranged on a chassis of the recording and/or reproducing apparatus. The disc tray is movable along the supporting shaft between an unloading position, protruding from the main body of the apparatus and a loading position substantially facing a disc driving unit within the main body of the apparatus on the chassis. The disc tray is movable by a driving mechanism, such as an electric motor. The disc tray on which the recording disc is set and which has been moved to the loading position has reached the position in which the recording disc is in register with the disc driving unit. The recording disc positioned in register with the disc driving unit is loaded on the driving unit. Thus the recording disc is held by the rotation mechanism and thereby run in rotation for recording/reproducing the information signals by an optical pickup unit.
Among the disc recording and/or reproducing apparatus having a rotary table, there is such an apparatus in which a selected one of plural recording discs may be retrieved for recording/reproduction by the disc driving unit. In this type of the disc recording and/or reproducing apparatus, an apparatus is proposed in which a disc tray carries a rotary table on which plural recording discs are set in parallel, as disclosed for example in U.S. Pat. Nos. 4,755,978 and 5,123,005. The rotary table is substantially disc-shaped and rotatable supported relative to the disc tray. The upper surface of the rotary table is formed with plural disc-setting recesses arrayed on the circumference of a circle having the center of rotation of the rotary table as its center. These disc-setting trays are arrayed at an equiangular distance about the center of rotation of the rotary table. The rotary table is rotated relative to the disc tray by a driving mechanism, such as an electric motor, mounted on the disc tray.
When the disc tray is at the loading position, the rotary table is rotated relative to the disc tray for selectively moving one of the recording discs set thereon to a position in register with the disc drive unit.
Among the disc recording and/or reproducing apparatus having a rotary table, there is an apparatus in which, when a recording disc is set on the disc drive unit, the disc tray may be moved to an unloading position. With this type of the disc recording and/or reproducing apparatus, when a recording disc set in one of the disc setting recesses has been loaded on the disc drive unit, the disc tray is moved to the unloading position for setting other recording discs on other disc setting recesses or exchanging the discs set in such other disc setting recesses. Therefore, with such disc recording and/or reproducing apparatus, the information signals may be continuously recorded on and/or reproduced from a number of the recording discs larger than the number of the disc setting recesses formed on the rotary table. If, with the disc recording and/or reproducing apparatus in which the disc tray is designed to be moved to the unloading position during loading of the recording disc on the disc drive unit, the disc tray is moved to the unloading position when a recording disc has been set on the disc drive unit, the disc tray is drive-controlled so that it may again be moved to the loading position on the proviso that the rotational angular position of the rotary table when the disc tray was at the loading position is maintained and that there is no other recording disc set on the disc setting recess on which the recording disc loaded on the disc drive unit was set.
With the above-described disc recording and/or reproducing apparatus, having the disc tray, there is a risk that, if the recording disc is rotated during the time the disc tray is at the loading position, the disc tray may oscillate with respect to the chassis in resonance with the oscillations caused with the rotation of the recording disc. Such resonant oscillations tend to produce abnormal sounds or obstruct the normal recording/reproducing operation of the pickup unit.
Among the conventional disc recording and/or reproducing apparatus, there is such an apparatus which is provided with a holding mechanism for holding the disc tray in association with the operation of holding the recording disc by the disc drive unit for suppressing any oscillation of the disc tray. Such a holding mechanism complicates the structure and renders it difficult to simplify the construction and to reduce the size of the disc recording and/or reproducing apparatus in its entirety.
Also, with the disc recording and/or reproducing apparatus which is provided with the rotary table and in which the disc tray may be moved to the unloading position when a recording disc is loaded on the disc drive unit, the disc tray which is set to the unloading position during the rotation of the recording disc tends to oscillate in resonance with oscillations caused by the recording disc rotation.
Among the disc recording and/or reproducing apparatus, there is an apparatus in which a pre-loading force tending to bias the disc tray against a supporting shaft is applied to the disc tray for suppressing resonant oscillations of the disc tray. Such pre-loading force tends to increase the load against the movement of the disc tray along the supporting shaft and the sliding noise between the disc tray and the supporting shaft and to enlarge the size of the drive mechanism.
On the other hand, with the disc recording and/or reproducing apparatus which is provided with a rotary table and in which the disc tray may be moved to the unloading position when a recording disc is set on the disc drive unit, the rotary table tends to rotate under an external pressure.
Above all, since the control for the driving mechanism is not in operation during power off, the rotary table may be rotated under the external pressure. If the recording disc is set on the rotary table, it is possible for the disc tray to rotate back to the loading position under the external pressure even in cases where a recording disc is loaded on the disc drive unit and another recording disc is set in the disc setting recess positioned in register with the disc drive unit. In such case, there is a risk that the recording disc loaded on the disc drive unit and the other disc set on the rotary table will collide against each other and cause damage or destruction of the discs.